Interchangeable tip-open cell fluorometer

ABSTRACT

Described and claimed is an interchangeable tip-open cell fluorometer comprising a housing and a fluorometric probe tip interchangeably connected to the housing, the probe tip including a probe tip housing defining an open cell and enclosing a probe optical arrangement, the probe optical arrangement including an excitation source and a fluorescence detector wherein the excitation source is aimed directly into the fluorescence detector such that a sample can be fluorometrically detected. Also claimed is a method of using this interchangeable tip-open cell fluorometer for detecting fluorescent signals emitted by one or more fluorophores from samples from a natural or industrial water system. The fluorometer, when coupled with a controller, is capable of monitoring and optionally controlling an industrial process or system.

FIELD OF THE INVENTION

The present invention relates generally to analytical devices andmethods for monitoring and/or controlling natural or industrialprocesses or systems. More specifically, the present invention relatesto an interchangeable tip-open cell fluorometer for detectingfluorescence emitted by a sample derived from a natural or an industrialprocess or system such that the process or system can be monitored and,optionally, controlled.

BACKGROUND OF THE INVENTION

A fluorometer is an analytical device that essentially comprises a lightsource, a means of selecting the desired excitation wavelength range, asample cell, a means of selecting the desired emission wavelength range,and a detector. A spectrofluorometer is a specific type of fluorometerwhere the means for selecting the excitation and/or emission wavelengthrange is performed by a grating. A grating acts to disperse a continuumof light into its components. Spectrofluorometers may be furthersubdivided into scanning spectrofluorometers, those that use amechanical means to scan the wavelength spectrum based on the positionof the grating relative to the excitation source and/or emission (thisdescribes a standard laboratory model fluorometer), or fixedspectrofluorometers where the grating is fixed with respect to theemission. The emission (fluorescence) is then directed to an array ofdetectors. The array of detectors could be charge coupled devices,usually abbreviated “CCD” or the array of detectors could bephotodiodes. The detectors are then calibrated in the appropriatewavelength units. A commercial device such as this is available fromOcean Optics (available from Drysdale and Associates, Inc., P.O. Box44055, Cincinnati, Ohio 45244 (513)831-9625). This type of fixedspectrofluorometer still requires the appropriate excitation wavelengthselection device, which could be a grating or filter.

The fluorometers that are most suitable for use under field conditionsare not grating spectrofluorometers, rather, they are filter-basedfluorometers. A filter-based fluorometer uses a filter to exclude allbut the selected wavelength range. In general, currently available andknown filter-based fluorometers have one channel with this channelcontaining an optically appropriate cell.

A light source and an optional excitation filter, are positioned on oneside of the optically appropriate cell, and an emission detector and anemission filter are positioned on another side of the opticallyappropriate cell. A reference detector may optionally be present.Because fluorescence is isotropic, in general, fluorometers areconfigured to detect any fluorescent light emitted from the fluorophoreat a 90° angle from the light source in order to minimize collection ofany spurious excitation light.

The excitation filter permits light of the chosen excitation wavelengthrange to pass through the filter and into the cell. When conductingoff-line batch testing, a sample of, for example, water from a naturalor an industrial water system is placed and held in the opticallyappropriate cell. When conducting on-line testing, the sample of watercan flow through the optically appropriate cell. The light is absorbedby a fluorophore present in the water sample, which, in turn, emits afluorescent light (hereinafter known as a fluorescent signal) having thesame or a longer wavelength than the excitation light. The emissionfilter, which is positioned between the emission detector and theoptically appropriate cell, is chosen so as to permit only the lightemitted by the fluorophore (the fluorescent signal of the fluorophore)to pass through the filter to the emission detector.

The use of fluorophores in industrial water systems or in hydrology ingeneral is known. The use of inert fluorescent tracers for determiningthe hydraulic losses in an industrial water system is known.Furthermore, using fluorescent tracers for controlling additive orproduct dosage to a recirculating or once-through cooling water systemis also known (see U.S. Pat. No. 4,783,314). In this method, afluorescent tracer is combined with one or more additives in a knownproportion of tracer to additive(s) and then the mixture is added to thewater of a cooling system. A fluorometer is then used to detect thepresence and concentration of the fluorescent tracer in the coolingwater and therefore the presence and concentration of the amount ofadditive.

There will always be a continuing need for new and improved fluorometersto be available for use in the challenging area of monitoring andcontrolling industrial water processes.

SUMMARY OF THE INVENTION

The first aspect of the instant claimed invention is an interchangeabletip-open cell fluorometer comprising:

-   -   a housing and a fluorometric probe tip interchangeably connected        to the housing, the probe tip including a probe tip housing        defining an open cell and enclosing a probe optical arrangement,        the probe optical arrangement including an excitation source and        a fluorescence detector wherein the excitation source is aimed        at the fluorescence detector such that a sample can be        fluorometrically detected.

The second aspect of the instant claimed invention is a method offluorometrically detecting fluorophores present in a sample, the methodcomprising the steps of:

a) providing a fluorometer, the fluorometer comprising

a housing and a fluorometric probe tip interchangeably connected to thehousing, the probe tip including a probe tip housing defining an opencell and enclosing a probe optical arrangement, the probe opticalarrangement including an excitation source and a fluorescence detectorwherein the excitation source is aimed at the fluorescence detector suchthat a sample can be fluorometrically detected;

b) providing one or more samples derived from a natural or industrialprocess stream;

c) using the fluorometer to detect the fluorescent signals of thefluorophores in the samples; and

d) operating a controller in such a way that the fluorescent signalsdetected by the fluorometer are used by the controller to monitor and/orcontrol the natural or industrial process from which the samples aretaken.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut away sectional view of an interchangeable probe tip fora fluorometer made in accordance with the present invention.

FIG. 2 is a cut away sectional view of another interchangeable probe tipfor a fluorometer made in accordance with the present invention.

FIG. 3 is a cut away sectional view of yet another interchangeable probetip for a fluorometer made in accordance with the present invention.

FIG. 4 is a cut away sectional view of still yet another interchangeableprobe tip for a fluorometer made in accordance with the presentinvention.

FIG. 5 is a sectional view of an interchangeable probe tip fluorometermade in accordance with the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Throughout this patent application the following words have theindicated meanings:

A “fluorophore” is: a molecule that, upon absorption of a photon ofenergy (hv) that results in an electron being promoted from themolecular electronic ground state (S₀) to an electronic excited state(S₁ or S₂ or S₃) and subsequently relaxing to the lowest vibronic stateof excited state S₁, emits a photon of energy “E” (hv) that is lower inenergy (though longer in wavelength) than was absorbed. Note that thisrelationship can be illustrated with the equation:E_((absorption))>E_((fluorescence)). This emission of energy results inthe molecular electronic state being returned to the ground state (S₀).The overall process results in emission of fluorescent photons in anisotropic distribution. The fluorophores capable of being detected bythe instant claimed fluorometer must be capable of absorbing excitationlight in the wavelengths of from about 200 nm to about 1200 nm andemitting it at a longer wavelength than the excitation light.

“Inert” refers to the fact that an inert fluorophore is not appreciablyor significantly affected by any other chemistry in the cooling watersystem, or by the other system parameters such as metallurgicalcomposition, microbiological activity, biocide concentration, heatchanges or overall heat content. To quantify what is meant by “notappreciably or significantly affected”, this statement means that aninert fluorophore has no more than a 10% change in its fluorescentsignal, under conditions normally encountered in cooling water systems.Conditions normally encountered in cooling water systems are known topeople of ordinary skill in the art of cooling water systems.

“Isotropic” refers to the fact that if a moiety is considered a pointsource, and excitation light is directed at the moiety, fluorescentlight is emitted equally in all directions, creating, in effect, asphere in 3 dimensions.

“nm” means nanometers; which are 10⁻⁹ meters.

The present invention provides an interchangeable tip-open cellfluorometer. This interchangeable tip-open cell fluorometer includes oneor more probe tips that can be interchangeably used with respect to thesame fluorometer. At least one of the probe tips includes an opticalarrangement that allows for the fluorometric detection of a sample in ameasuring cell associated with the fluorometer such as a measuring cellin an open or flow cell configuration. In general, the probe tip opticalarrangement includes an excitation source and a fluorescence detectorsuch that excitation source is aimed at the fluorescence detector, suchas directly at the detector in a 180° arrangement or substantiallyapproximate 180° arrangement. This effectively provides a sleek andsimple design that can be effectively used to detect, monitor and/orcontrol industrial or natural streams based on a fluorometricmeasurement from a sample derived from same. It should be appreciatedthat the present invention contemplates an arrangement with respect tothe excitation source and the fluorescence detector that can deviatefrom a 180° arrangement as described below in greater detail.

The interchangeable tip-open cell fluorometer of the present inventioncan provide a low-cost alternative to conventional fluorometers. In anembodiment, the fluorometer of the present invention is provided in aflashlight-style that can be hand-held and shaped in any suitable way,such as a cylindrical tube shape. In this regard, a measurement can betaken by dipping the interchangeable tip of the fluorometer of thepresent invention into a process water sample, for example, coolingwater treated with treatment chemicals and using fluorometers fordetecting fluorophores, pushing a button, and reading the product level,such as in parts per million (ppm) on a display.

With this fluorometer, the design emphasis is on minimal cost for smallaccounts and ease of use for unskilled operators. The cylindricaltube-shape has many desirable functional features including batteryoperation, numerical readout, two-point calibration, compensation forsample temperature, turbidity, and fouling of the optical surfaces,communications to Palm computer or the like for downloading of storeddata, a unique, self-identifying fluorometer probe tip and the like. Thefluorometer of the present invention can be made with a process controloutput and connector, for controlling a chemical feed pump, data loggingand/or for performing other suitable process monitoring and/or controlactivities. For example, the fluorometer of the present invention can beadapted to alert the user when cleaning of the tip is required.

An important aspect of the present invention is the interchangeableprobe tip. In general, the probe tip provides a small, self-containedfluorometer with built-in optics and circuitry, such as for typeidentification, detectors, light sources, temperature measurement andthe like. The probe tip is constructed such that it is readily pluggableinto the fluorometer housing. This makes it easily replaceable withanother probe tip whenever a different probe tip with different opticsis necessary to account for changes in the sampling environment, such asfor measuring the fluorescence derived from different fluorophores, tipdamage and/or the like. Upon replacing one interchangeable tip foranother interchangeable tip, the fluorometer is ready-for-use withminimal, or effectively no, added effort required from the operator.This is a huge practical advantage of the instant claimed invention,especially when compared to the effort required to set up and use twodifferent fluorometers.

In this regard, the probe tip contains virtually all of the electronicsand optics to perform the fluorescence measurements. For example, propergain can be built into the electronic configuration associated with theprobe tip, thus relieving the main unit from having to adjust gainsettings. Further, noise interferences can be minimized by having theelectronics inside of the probe tip. The excitation source, such as alight emitting diode (LED) source, can be configured to have its ownseries resistor so that the main unit does not have to regulate LEDcurrent.

The probe tip also optionally can include a thermistor. It is preferredthat the probe tip include a thermistor to measure sample temperaturefor correction of fluorescence intensity. By choosing differentthermistor resistances based on, for example a temperature of 25° C.,the probe tips are effectively self-identifying without added cost orcomplexity. In other words, each probe tip can include a thermistor witha resistance that is specific to the respective probe tip. Once theprobe tip is plugged into the fluorometer housing and the thermistorresistance is made known, the specific optical and electronicarrangement with respect to the probe tip can be identified, thusallowing the interchangeable tip-open cell fluorometer to beready-for-use.

As previously discussed, the probe tip has an optical arrangement thatprovides a linear and slim profile for the fluorometer. In this regard,the excitation source of the probe tip is aimed at the fluorescencedetector. For example, the excitation source and/or the light that emitstherefrom and the fluorescence detector can be configured in a 180°arrangement or acceptable deviations thereof. This is different fromconventional one-channel-sample fluorometers where detection of thefluorescent light emitted from the fluorophore is at a 90° angle fromthe light source as previously discussed. Based on these differences,the interchangeable tip-open cell fluorometer of the present inventioncan provide a number of advantages over conventional one-channel-samplefluorometers including, for example, a sleek and simple design,selectable sensitivity, accurate compensation for turbidity and windowfouling, and the like as described below.

The fluorometer of the present invention makes use of a specific type ofoptical filters, such as a thin-film optical filter with the requisiteoptical, mechanical and chemical properties necessary to enhance thefluorescent detection capabilities. The physical attributes of thefilters can also enhance the detection sensitivity as compared toquartz, glass sample cells, cuvettes or the like that can contribute tounwanted light scattering such that the sensitivity and concentrationrange can be reduced. In this regard, the measured sample is in directcontact with the filters that define the measuring volume. Thus the useof the term “open cell” as a descriptor of the fact that it is thefilters themselves that form the outer boundaries of the sample cell andthere is no other structure involved in the sample cell, except for theouter walls of the housing itself.

The filters are required to be made from a material or combination ofmaterials that are chemically inert and provide a hard surface such thatchemical and brush cleaning of the cell can be performed when it becomesnecessary. By designing the optical filters for a water interface on thesample side and air interface on the internal side, performance of thefilters can be optimized for analyzing low levels of fluorophores.

The fluorometer of the present invention can include a variety ofdifferent components fashioned in any suitable configuration dependingon the application. It can be configured as a stand alone unit or it canbe interfaced with one or more additional process components formonitoring and/or control purposes in any known and suitable way. Theinterchangeable tip-open cell fluorometer can be adapted for detectionpurposes in any suitable way, such as for grab sampling purposes,in-line detection, in-process detection and/or the like.

In general, the fluorometer includes a fluorometric probe tip that isinterchangeably connected to a housing. The fluorometric probe tipincludes an excitation light source. The excitation source can includeany suitable type of light source, such as a monochromatic light source,polychromatic light source and the like. For example, the excitationsource can include a LED source, a laser source and the like. The LEDsource can emit light of varying wavelengths, such as an IR LED, a UVLED, a blue LED and/or the like.

The excitation source generates a collimated beam of excitation light.The excitation light passes through a filter in the probe tip and into ameasuring cell with an open-cell configuration defined by the probe tiphousing and the surface of the excitation light filter and the surfaceof the emission light filter. The sample is in direct contact with thefilters as previously discussed. This allows the excitation light toproject into the sample within the measuring cell whereupon fluorescenceis produced due to the presence of one or more fluorophores in thesample. The emitted fluorescence then passes through an additionalfilter and is directed to a fluorescence detector for detectionpurposes. The additional filter also acts to effectively block theexcitation light from passing to the fluorescence detector. This allowsthe fluorescence of the sample to be measured with precision,sensitivity and accuracy despite the fact that the excitation light isdirected at the fluorescence detector, such as directly at thefluorescence detector in a 180° optical arrangement. As previouslydiscussed, this optical arrangement provides a number of advantages ascompared to fluorometers that use a conventional 90° opticalarrangement.

The sample can emit fluorescent light due to the presence of one or morefluorophores within the sample as discussed above. Regarding thedescription of the fluorophores capable of being detected by the instantclaimed fluorometer, it is necessary to note that in order to bedetectable by the instant claimed fluorometer, the fluorophore must becapable of absorbing light in the wavelengths of from about 200 nm toabout 1200 nm and emitting it at a slightly longer wavelength.Preferably, the fluorophores absorb light in the wavelengths of fromabout 350 nm to about 800 nm. The fluorescence detector measures anamount of fluorescence that can be correlated to a concentration of thefluorophore in the sample. In an embodiment, the fluorescence detectorcan measure an intensity of the fluorescence that can be equated to aconcentration of the fluorophore as generally understood to one of skillin the art.

The filters can be made of any suitable material. In general, theoptical, mechanical and chemical properties of the filter are providedand required as follows according to an embodiment. With respect tooptical properties, the filters are required to have a hightransmittance in pass band areas for the excitation light (i.e., UV LED)or the emitted fluorescence. As mentioned above, the first filteressentially allows all of the excitation light to pass therethrough andinto the sample. Then, the emitted fluorescence from the sample can passthrough the second filter all the while the excitation light iseffectively blocked from passing through the second filter andinevitably to the detector. Thus, this ensures that the interferenceeffects of the excitation light with respect to the fluorescentmeasurement are effectively eliminated, or at least greatly reduced.This effect can be further enhanced if the pass bands of the filters aresharp and deep cut.

If a second light source is used, the optical properties of the filtersallow the second light in a sufficient amount to pass through bothfilters and at a different wavelength than the light emitted from theexcitation source. In this way, the second light source can be used tocorrect for fouling, turbidity and/or other like effects that canadversely impact the detection capabilities of the fluorometer asdescribed in greater detail below.

With respect to mechanical properties, the filter includes an exposedsurface that is hard such that it can withstand general use, such ascleaning, brushing, abrasive particles in the sample and the like. Thisis an important quality due to the fact that the filters act to definethe open cell configuration of the measuring cell according to anembodiment of the present invention. In this regard, the sample is indirect contact with the filters and thus must be able operateeffectively under normal process conditions. The filters are alsoeffectively chemically inert. In this way, the filters should not bereactive, such as with respect to the sample, cleaning solutions and thelike. Having the filters define the measuring cell, light scattering dueto glass sample cells in conventional fluorometers is effectivelyeliminated.

The filters can also be used to adjust the sensitivity of thefluorescent detection. In this regard, the distance between the filterscan be varied and thus effectively acts to adjust sensitivity. This maybe useful if the measured samples may require different levels ofdetection sensitivity. For example, a more concentrated sample offluorophores may require a lower sensitivity to enhance detectioncapabilities. In this regard, the spacing between the filters can bedecreased to create less volume of measured sample, thus lowering thesensitivity with respect to the detection of same. For less concentratedsamples, the spacing may be increased to increase sensitivity. Thus, thepresent invention can be readily adapted to adjust for varying levels ofsensitivity depending on the application. This sensitivity adjustmentcannot be achieved with the conventional 90° optical arrangement.

Preferably, the filter includes a layered structure. In general, thefilter provides a low pass filter layer and a high pass filter layerthat are separated by a substrate layer, such as a glass substrate. Thisstructure allows for the fluorescence emission to pass to the detectorvia the filter while the excitation light is effectively blocked fromdoing so. The filters are commercially available as Brightline™ atSemrock, Incorporated, 3625 Buffalo Road, Suite 6, Rochester, N.Y. 14624(585)594-7017. It should be appreciated that a commercially availablefilter material may be required to be modified and customized withrespect to the optical, mechanical and chemical properties of the filterdepending on the application.

The interchangeable probe tip can include additional other and suitablecomponents that can further enhance its detection capabilities. Forexample, the probe tip can include a reference detector. This is used tomeasure a portion of the excitation light source during fluorescentdetection. In this regard, the reference detector can be used tocompensate for variations in the excitation light emission due to, forexample, changes in current associated with the excitation light source,temperature changes, aging, device to device variability, productiontolerances and/or the like. This can be done in a number of suitableways. For example, the fluorescent measurement associated with thefluorescence detector can be divided by the reference detectormeasurement to provide a normalized fluorescent measurement. This, inessence, subtracts outs the variation effects with respect to theexcitation light source as discussed above. In an embodiment, thereference detector and the fluorescence detector include the same typeof detector. This effectively alleviates any variability in detectionbetween the reference detector and the fluorescence detector that may bedue differences in the type of detector that is used. It should beappreciated that the reference detector can also be applied toeffectively eliminate any variability in the second light source in anysuitable way, such as in a similar way as discussed above with respectto the excitation light source.

Further, the interchangeable probe tip can include an aperture. Theaperture can be made of any suitable material and sized and configuredin any suitable way including a cylindrical tube shape. In anembodiment, the fluorescence emission passes to the detector via theaperture. In this way, the aperture can be effectively sized and shapedto minimize the effects of turbidity on the fluorescent detectioncapabilities of the fluorometer. Turbidity can cause light scatteringthat can be detected and thus interfere with the fluorescentmeasurement. As the aperture size is decreased, this should minimizelight scattering effects due to turbidity. However, the aperture sizeshould not be too small such that the emitted fluorescence or sufficientportion thereof is prevented from passing to the fluorescence detector.

In an embodiment, the interchangeable probe tip includes two lightsources, an excitation light source and a second light source that doesnot induce fluorescence. The second light source can be used to correctfor effects on the fluorescent measurement due to fouling, turbidityand/or the like. The excitation source is dedicated for directfluorescence measurement. This source emits a collimated beam of lightinto the sample whereupon fluorescence is emitted based on the amount offluorophore in the sample. The fluorescence emission then passes to thefluorescence detector via the filter where the excitation light iseffectively blocked from passing to the fluorescence detector aspreviously discussed.

Once fluorescent detection has been made, the excitation source isturned off and the second light source is turned on. The light emittedfrom the second light source is a different wavelength than the lightemitted from the excitation source so as not to induce fluorescence. Inan embodiment, the excitation source includes a UV LED, and the secondlight source includes an IR LED. The second light source emits lightinto the fluorescence detector via the filters and sample. The secondlight emission is preferably directed along a path that corresponds tothe same path along which the light from the excitation source waspassed. In an embodiment, the first and second light emissions passalong the same or substantially the same path. This allows the secondlight, once detected, to provide an accurate indication that correspondsto the amount of fouling, turbidity and/or other effects on thefluorescent measurement. In this way, the fluorescent measurement can becorrected in any suitable manner to account for such effects, thusenhancing the fluorescent detection capabilities. These correctionscannot be done with the conventional 90° optical arrangement.

Alternatively, the first and second light emissions can deviate from anemission path that is the same or substantially the same. Thus, thefirst and second light emissions can be configured to pass in sufficientportion along the same path such that correction with respect tofouling, turbidity and/or the like can be effectively, though lessaccurately, made. It should be appreciated that the first and secondlight sources can be configured in a number of suitable and differentways, some of which are described in greater detail below.

As previously discussed, the interchangeable tip-open cell fluorometerof the present invention can be configured in a number of suitable ways.As detailed below, a number of examples of the interchangeable probe tipare provided illustrative of the present invention.

EXAMPLES Example One Interchangeable Probe Tip with Normal, ParallelBeam Configuration

Turning to FIG. 1, an embodiment of the present invention isillustrated. The interchangeable probe tip 10 includes an excitationlight source 12 and a second light source 14. The excitation source 12includes an ultraviolet light emitting diode 16 (UV LED). The excitationsource 12 emits a collimated excitation light beam 18 that is directedat a reflective member 20, such as a dichroic mirror or the like, asshown in FIG. 1. The reflective member 20 is reflective with respect toa substantial amount of the excitation light beam 18, such as about 98%reflective or less. The reflective member 20 is also transmissive withrespect to the remaining portion of excitation light beam, such as about2% transmissive or greater. The reflected portion 22 of excitation lightassociated with the excitation light source 12 is directed to a firstfilter 24 at an angle that is perpendicular or substantiallyperpendicular with respect to the first filter 24. The excitation lightbeam 26 passes into a measuring cell 28 where the sample 30 is providedin an open cell arrangement. The projection of the excitation light 26causes a fluorescence emission 32 based on an amount of fluorophore inthe sample 30. The fluorescence emission 32 passes through a secondfilter 34 and into a fluorescence detector 36 via an aperture 38 thathas an opening 40 sized to receive the collimated beam of fluorescenceemission 32 in at least a substantial amount. The fluorescence detector36 then acts to measure the amount of fluorescence which can becorrelated in any suitable manner to a concentration of the targetfluorophore or fluorophores in the sample for monitoring and/or controlpurposes.

To enhance the detection capabilities of the fluorescent detection, theinterchangeable probe tip includes a reference detector 42 that receivesa portion of the excitation light 18 via the reflective member 20 aspreviously discussed. The reference detector 42 can be used tocompensate for variations in the excitation light emission as discussedabove.

The interchangeable probe tip 10 further includes a second light source14 that is used for corrective purposes with respect to fouling,turbidity and/or the like as discussed above. The second light source 14includes an IR LED source. This generates a collimated beam of light 46that is directed to the reflective member 20. A substantial amount ofthe beam 46 is transmitted through the reflective member 20, as lightbeam 48, along the same or substantially the same path as the reflectedexcitation light beam 22. In an embodiment, about 98% or more of thelight beam is transmitted through the reflective member 20 and into themeasuring cell 28. The remaining portion of light beam 50 associatedwith the second light source 14 is reflected via the reflective member20 into the reference detector 42 to compensate for variations in thesecond light source emission similar to the excitation source emissionas previously discussed.

The transmitted amount of light beam 48 from the second light source 14passes through the sample 30 and further passes through the secondfilter 34 in at least a substantial amount along the same orsubstantially the same path that the fluorescent emission 32 passesthrough the second filter 34. The amount of transmitted light associatedwith the second light source is then detected by the fluorescencedetector 36. This measurement can be used in any known way to correctfor changes in the fluorescent measurement due to fouling, turbidityand/or the like as previously discussed.

Example Two Interchangeable Probe Tip with Straight-Through BeamConfiguration

Turning to FIG. 2, another embodiment of the interchangeable probe tipaccording to the present invention is provided. The interchangeableprobe tip 60 includes a single light source 62 that includes a UV LEDsource. The excitation source 62 emits a collimated light beam 64through a first filter 66 and into a measuring cell 68 where the sample70 is located. This causes fluorescence associated with an amount offluorophore in the sample. The fluorescence emission 72 passes through asecond filter 74 and into a fluorescence detector 76 for detectionpurposes. The fluorescence emission 72 passes through an aperture 78 tominimize the effects of turbidity on the detectable fluorescence. Theaperture 78 is sized such that all or a substantial portion of thefluorescence emission passes therethrough and into the detector. Theinterchangeable probe tip further includes a reference detector 80 thatcan be used to measure a portion of the light derived from theexcitation source. As previously discussed, this can be then used toaccount for variations in the excitation light source.

Example Three Interchangeable Probe Tip with Double Angle BeamConfiguration

Turning to FIG. 3, another embodiment of the interchangeable probe tipis provided. The interchangeable probe tip 90 includes an excitationsource 92 that includes a UV LED source. This is used to measurefluorescence in a sample 94 within a measuring cell 193 in a similarfashion as provided in EXAMPLE TWO. In this regard, the excitation lightsource 92 emits a collimated beam of light 96 into the sample 94 via afirst filter 98 such that a fluorescence emission 100 is generated andthen passes through a second filter 102 into a detector 104 via anaperture 106. The excitation light 96 is effectively blocked out or atleast a substantial portion thereof from passing into the detector 104due to the optical features of the filters as discussed above. Thus, thefluorescent measurement can be taken with minimal, if any, effect due tothe excitation light. The probe tip further includes a referencedetector 107 that detects a portion of the excitation light derived fromthe excitation source. This can also enhance the detection capabilitiesof the probe tip as previously discussed.

Further, the probe tip 90 includes a second light source 108. The secondlight source 108 includes an IR LED that generates a collimated beam oflight 110. The light 110 passes through the first filter 98 at an angleoffset from perpendicular to the first filter. For example, the angle isoffset at about 12° or less from perpendicular or normal. In this way,the second source of light 110 passes through the sample, through thesecond filter 102 and into the detector 104 via the aperture 106 along apath that corresponds in a sufficient amount to the path through whichthe excitation light and fluorescent emission has passed. The detectorthen can measure the intensity of the second light source which can beused for corrective purposes as previously discussed. This demonstratesthat the second source of light does not necessarily have to pass alongthe same path as the source of excitation light and/or emissiontherefrom in order to effectively act for corrective purposes due tofouling, turbidity and/or the like. Reference detector 107 can be usedto measure a portion of the light from light source 108 to account forvariations in light source 108.

Example Four Interchangeable Probe Tip with Compound Angle BeamConfiguration

Turning to FIG. 4, another embodiment illustrative of theinterchangeable tip is provided. In general, this example providesanother variation regarding the positioning with respect to a pair oflight sources that can be used to enhance the fluorescent detectioncapabilities of the interchangeable probe tip.

The interchangeable probe tip 120 includes an excitation source 122 thatincludes a UV LED source. This is used to measure fluorescence in asample 124 within a measuring cell 126. In this regard, the excitationlight source 122 emits a collimated beam of light 128 into the sample124 via a first filter 130 such that a fluorescence emission 131 isgenerated and then passes through the second filter 132 into a detector134 via an aperture 136. The excitation light 128 passes through thefirst filter 130 at an angle offset from perpendicular, such as about 9°or less. The excitation light 128 is effectively blocked out or at leasta substantial portion thereof from passing into the detector 134 due tothe optical features of the filters as discussed above. Thus, thefluorescent measurement can be taken with minimal, if any, effect due tothe excitation light.

Further, the probe tip 120 includes a second light source 137. Thesecond light source 137 includes an IR LED that generates a collimatedbeam of light 138. The light 138 passes through the first filter 130 atan angle offset from perpendicular, such as about 9° or less withrespect to the first filter 130. In this way, the second source of light138 passes through the sample 124, through the second filter 132 andinto the detector 134 via the aperture 136 along a path that correspondsin a sufficient amount to the path through which the fluorescentemission passed. The detector 134 then can measure the intensity of thesecond light source which can be used for corrective purposes aspreviously discussed. This further demonstrates that the second sourceof light does not necessarily have to pass along the same path as thesource of excitation light and/or emission therefrom in order toeffectively act for corrective purposes due to fouling, turbidity and/orthe like.

The probe tip 120 further includes a reference detector 140 that detectsa portion of the excitation light derived from the excitation source.This can also enhance the detection capabilities of the probe tip aspreviously discussed. Reference detector 140 can be used to measure aportion of the light from light source 137 to account for variations inlight source 137.

Example Five Self-Identifying Interchangeable Tip-Open Cell Fluorometer

As previously discussed, the fluorometer of the present invention has aself-identifying feature that allows the fluorometer to be ready-for-useonce one probe tip is interchanged with another probe tip. Turning toFIG. 5, the fluorometer 150 includes a housing 152 and a probe tip 154.The housing electronics (not shown) can be configured in any suitableway to power the fluorometer 150. In this regard, the fluorometer can bebattery operated. In the alternative, the fluorometer can be operated byan external power source that is electrically connected to thefluorometer, such as through the housing. The housing 152 can include adisplay 156 for monitoring the fluorescent measurements. At least anumber of the functions of the fluorometer can be automated, such asthrough a switch. For example, the housing 152 can include an on/offswitch 158 and a calibration switch 160 for operation in calibrationmode as shown in FIG. 5. The wiring from the electronics of the housing152 leads to an electrical connector 162 of any suitable type.

The interchangeable probe tip 154 has a housing 164 with an opening 166that defines a measuring cell 168 within which a sample 170 can befluorometrically measured as previously discussed. The probe housingencloses the optics and electronics of the probe tip which can beconfigured in any suitable way such as illustrated above. The wiring ofthe electronics, such as the leads 169 to the detectors, light sourcesand the like connect to the electrical connector 172 of the probe tip154. This allows the probe tip 154 to be pluggable into the housing 152via mating of the electrical connector 172 of the probe tip 154 and theelectrical connector 162 of the housing 152.

Once the probe tip is plugged into the housing, the fluorometer iseffectively ready for use. The probe tip includes a thermistor (notshown). The optical and electronic arrangement of the probe tip isassociated with a respective thermistor that has a specific resistanceas previously discussed. This allows the fluorometer to recognize whattype of probe tip is being used once a probe tip has been interchangedwith another probe tip, thus enabling it ready for use.

It should be appreciated that the self-identifying property of theinterchangeable tip-open cell fluorometer can be configured in anysuitable way. For example, the self-identifying features of the presentinvention can include the same or similar features with respect to the“smart” probe as disclosed in U.S. Pat. No. 6,556,027 that issued onApr. 29, 2003, which is herein incorporated by reference in itsentirety.

The interchangeable probe tip can include any suitable type of opticaland electrical arrangement for purposes of fluorescent detection,examples of which have been discussed above. In addition tofluorescence, the fluorometer can be adapted to take additional othermeasurements, such as with respect to turbidity, colorimetry and thelike. In this regard, the turbidity and colorimetric measurements can betaken with a probe tip that has been configured specific to thatapplication. Thus, the present invention contemplates theinterchangeability of probe tips that can separately measurefluorescence, turbidity and colorimetry.

For example, the turbidity probe tip can be configured in a similar wayas the fluorometric probe tip as discussed above. The difference betweenthe two results in the type of light sources. For the turbidity probetip, the light source must not cause fluorescence. For highestsensitivity, the aperture is removed. Any suitable light source can beused, such as a UV LED, blue LED or the like. With the turbidity probetip, a blue light source is preferable. However, the fluorometric probetip can be interchanged with the turbidity probe tip and vice versagiven the self-identifying features as discussed above.

With respect to a colorimetric probe tip, this design is similar to thefluorometric and/or turbidity tip design except that only one filter isnecessary. The light source is chosen to correspond to an absorptionband of the material in the sample to be detected. In general, acolorimetric amount associated with the sample can be measured bypassing an excitation light source, such as a UV LED, though a firstfilter and then into a detector constructed for that particular type ofdetection.

It should be appreciated that the mirrors, filters, detectors,excitation light sources, and other suitable components can include avariety of different and suitable commercially available or knownproducts. For example, the detectors are commercially available fromHamamatsu Corporation, 360 Foothill Road, Bridgewater, N.J. 08807 (PartNo. S2386-44K); the UV LED source is commercially available from NichiaAmerica Corporation, 3000 Town Center Drive, Southfield, Mich. 48075(Part No. NSHU590A); and the IR LED source is commercially availablefrom Optek Technology, Inc., 1215 W. Crosby Road, Carrollton, Tex. 75006(Part No. OP265B).

The present invention can include a variety of different and additionalcomponents for optimizing process control, monitoring and/or automation.In an embodiment, the fluorometer includes a printed circuit boardassembly connected to a controller, each of a suitable and knownconstruction (not shown). For example, the controller is available fromTecnova, 1486 St. Paul Ave., Gurnee, Ill. 60031 (847)662-6260.

The printed circuit board (PCB) assemblies useful in this device must befabricated to allow powering by the controller or other device of thecomponents of the fluorometer, which include, for example, drivers forthe excitation sources and amplifiers to perform current-to-voltageconversion and signal amplification from the photodetectors. Circuitryto manipulate the signals and communicate the magnitude of the signalsis also integral to the PCB. Additional circuitry to measure thetemperature and/or the status of the flowswitch may be included.

The fluorometer can be further connected to the controller by acommunication cable that enables the controller to electronicallycommunicate with the fluorometer to control the components of thefluorometer as previously discussed. A suitable communication protocolmust be selected in order to operate the fluorometer. Suitable standardcommunication protocols include, but are not limited to, RS-232, I²C,CAN, TCP/IP and a standard RS-485 serial communication protocol. Thepreferred communication protocol is a standard RS-485 serialcommunication protocol. It is also possible to use a wirelesscommunication protocol between the fluorometer and controller. One suchsuitable wireless communication protocol is Bluetooth.

The controller can include isolated, multiple analog inputs. Theseinputs provide information based on their signal magnitude via 4–20 mAconnections. The signals are read by the analog inputs for controllinglogic of the controller to provide additional levels of control to, forexample, an industrial water system. In a preferred embodiment, thecontroller has twenty (20) discrete analog inputs.

As previously discussed, the fluorometer of the present invention can beused to monitor and/or detect the presence of one or more fluorophoresin a sample derived from any suitable process or system includingnatural water systems, industrial water systems, or other like sources.Industrial water systems include, but are not limited to, cooling towerwater systems (including open recirculating, closed and once-throughsystems); petroleum wells, downhole formations, geothermal wells andother oil field applications; boilers and boiler water systems; mineralprocess waters including mineral washing, flotation and benefaction;paper mill digesters, washers, bleach plants and white water systems;black liquor evaporators in the pulp industry; gas scrubbers and airwashers; continuous casting processes in the metallurgical industry; airconditioning and refrigeration systems; industrial and petroleum processwater; indirect contact cooling and heating water, such aspasteurization water; water reclamation and purification systems;membrane filtration water systems; food processing streams (meat,vegetable, sugar beets, sugar cane, grain, poultry, fruit and soybean);and waste treatment systems as well as in clarifiers, liquid-solidapplications, municipal sewage treatment and industrial or municipalwater systems.

The fluorometer of the present invention can be used in a variety ofdifferent industrial water system applications as disclosed, forexample, in the following U.S. patent applications.

The instant claimed fluorometer and controller are capable offunctioning to control a cooling water system, as described and claimedin U.S. Pat. No. 6,315,909 B1, entitled USE OF CONTROL MATRIX FORCOOLING WATER SYSTEMS CONTROL, issued Nov. 13, 2001, which is hereinincorporated by reference in its entirety.

The instant claimed fluorometer and controller are capable offunctioning to control a boiler, as described and claimed in U.S. Pat.No. 6,336,058 B1, entitled USE OF CONTROL MATRIX FOR BOILER CONTROL,issued U.S. Pat. No. 6,336,058 B1, issued Jan. 1, 2002, which is hereinincorporated by reference in its entirety.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. An interchangeable tip-open cell fluorometer comprising: a housingand a fluorometric probe tip interchangeably connected to the housing,the probe tip including a probe tip housing defining an open cell andenclosing a probe optical arrangement, the probe optical arrangementincluding an excitation source and a fluorescence detector wherein theexcitation source is aimed at the fluorescence detector such that asample in the open cell can be fluorometrically detected.
 2. Theinterchangeable tip-open cell fluorometer of claim 1 further comprisingan excitation filter and an emission filter each in contact with thesample.
 3. The interchangeable tip-open cell fluorometer of claim 2wherein the excitation filter includes an excitation band and theemission filter includes an emission band, and wherein the excitationband and the emission band are sufficiently separated such that at leasta substantial amount of a light beam derived from the excitation sourcecannot pass through the emission filter to the fluorescence detector. 4.The interchangeable tip-open cell fluorometer of claim 2 wherein theprobe optical arrangement includes a second light source in addition tothe excitation source that each emits a light beam to the sample via areflective member at an angle perpendicular to the excitation filter. 5.The interchangeable tip-open cell fluorometer of claim 4 wherein thereflective member includes a dichroic mirror.
 6. The interchangeabletip-open cell fluorometer of claim 4 wherein the second light sourceemits a light beam that can pass through the excitation filter and theemission filter allowing correction to the fluorometric detection due toat least one of fouling and turbidity.
 7. The interchangeable tip-opencell fluorometer of claim 2 wherein the excitation source includes asingle excitation source that passes an excitation light beam throughthe excitation filter thereby causing a fluorescent emission derivedfrom the sample, wherein the fluorescent emission passes through theemission filter for detection while the excitation light beam iseffectively blocked from passing therethrough, and wherein the singleexcitation source is aimed directly at the fluorescence detector.
 8. Theinterchangeable tip-open cell fluorometer of claim 2 wherein the probeoptical arrangement includes a second light source in addition to theexcitation source, wherein the excitation source emits an excitationlight beam at an angle perpendicular to the excitation filter, andwherein the second light source emits a second light beam at an angleoffset from perpendicular with respect to the excitation filter.
 9. Theinterchangeable tip-open cell fluorometer of claim 8 wherein the secondlight beam is offset at about 12° or less from perpendicular withrespect to the excitation filter.
 10. The interchangeable tip-open cellfluorometer of claim 8 wherein the second light beam can pass throughthe excitation filter and the emission filter such that fluorometricdetection can be corrected for at least one of turbidity and fouling.11. The interchangeable tip-open cell fluorometer of claim 2 wherein theprobe optical arrangement includes a second light source in addition tothe excitation source such that each passes through the excitationfilter at an angle offset from perpendicular with respect to theexcitation filter.
 12. The interchangeable tip-open cell fluorometer ofclaim 11 wherein the angle is approximately 9° or less.
 13. Theinterchangeable tip-open cell fluorometer of claim 1 further comprisingone or more additional probe tips in addition to the fluorometric probetip wherein the fluorometric probe tip can be used interchangeably withthe one or more additional probe tips.
 14. The interchangeable tip-opencell fluorometer of claim 13 wherein the fluorometric probe tip and theone or more additional probe tips are self-identifying allowing thefluorometer to be ready-for-use once a probe tip has been interchanged.15. The interchangeable tip-open cell fluorometer of claim 13 whereinthe one or more additional probe tips at least include a turbidity probetip and a colorimetric probe tip.
 16. A method of fluorometricallydetecting fluorophores present in a sample, the method comprising thesteps of: a) providing a fluorometer, the fluorometer comprising ahousing and a fluorometric probe tip interchangeably connected to thehousing, the probe tip including a probe tip housing defining an opencell and enclosing a probe optical arrangement, the probe opticalarrangement including an excitation source and a fluorescence detectorwherein the excitation source is aimed at the fluorescence detector suchthat a sample in the open cell can be fluorometrically detected; b)providing one or more samples derived from a natural or industrialprocess stream; c) using the fluorometer to detect the fluorescentsignals of the fluorophores in the samples; and d) operating acontroller in such a way that the fluorescent signals detected by thefluorometer are used by the controller to monitor and/or control thenatural or industrial process from which the samples are taken.
 17. Themethod of claim 16 further comprising an excitation filter and anemission filter each in contact with the sample.
 18. The method of claim17 wherein the excitation filter includes an excitation band and theemission filter includes an emission band, and wherein the excitationband and the emission band are sufficiently separated such that at leasta substantial amount of a light beam derived from the excitation sourcecannot pass through the emission filter to the fluorescence detector.19. The method of claim 17 wherein the probe optical arrangementincludes a second light source in addition to the excitation source thateach emits a light beam to the sample via a reflective member at anangle perpendicular to the excitation filter and along substantially thesame path.
 20. The method of claim 19 wherein the second light sourceemits a light beam that can pass through the excitation filter and theemission filter allowing correction to the fluorometric detection due toat least one of fouling and turbidity.
 21. The method of claim 17wherein the light source includes a single excitation source that passesan excitation light beam through the excitation filter thereby causing afluorescent emission derived from the sample, wherein the fluorescentemission passes through the emission filter for detection while theexcitation light beam is effectively blocked from passing therethrough,and wherein the single excitation source is aimed directly at thefluorescence detector.
 22. The method of claim 17 wherein the probeoptical arrangement includes a second light source in addition to theexcitation source, wherein the excitation source emits an excitationlight beam at an angle perpendicular to the excitation filter, andwherein the second light source emits a second light beam at an angleoffset from perpendicular with respect to the excitation filter.
 23. Themethod of claim 22 wherein the second light beam can pass through theexcitation filter and the emission filter such that fluorometricdetection can be corrected for at least one of turbidity and fouling.24. The method of claim 17 wherein the probe optical arrangementincludes a second light source in addition to the excitation source suchthat each passes a light beam through the excitation filter at an angleoffset from perpendicular with respect to the excitation filter.
 25. Themethod of claim 16 further comprising one or more additional probe tipsin addition to the fluorometric probe tip wherein the fluorometric probetip can be used interchangeably with the one or more additional probetips.
 26. The method of claim 25 wherein the one or more additionalprobe tips at least include a turbidity probe tip and a colorimetricprobe tip.
 27. The method of claim 16 wherein the sample is from thewater of an industrial process stream wherein the industrial processstream is an industrial water system.
 28. The method of claim 27 whereinsaid industrial process stream is selected from the group consisting of:cooling tower water systems; open recirculating cooling tower watersystems; closed cooling two water systems; once-through cooling towerwater systems; petroleum wells; downhole formations; geothermal wells;oil field based water system; boilers; boiler water systems; mineralprocess waters including mineral washing, flotation and benefaction;paper mill digesters; paper mill washers; paper mill bleach plants;paper mill white water systems; black liquor evaporators in the pulpindustry; gas scrubbers and air washers; continuous casting processes inthe metallurgical industry; air conditioning and refrigeration systems;petroleum process water; indirect contact cooling and heating water,such as pasteurization water; water reclamation and purificationsystems; membrane filtration water systems; food processing streams;waste treatment systems; clarifiers; liquid-solid applications;municipal sewage treatment; and industrial or municipal water systems.29. The method of claim 16, wherein step (c) is accomplished by amethodology selected from the group of consisting of: grab-sampling;in-line detection; and in-process detection.
 30. The method of claim 16,wherein said excitation source is selected from the group consisting of:a LED source; and a laser source.
 31. The method of claim 16, whereinsaid excitation source is capable of emitting light having a wavelengthfrom about 200 nm to 1200 nm.
 32. The interchangeable tip-open cellfluorometer of claim 1, wherein said excitation source is selected fromthe group consisting of: a LED source; and a laser source.
 33. Theinterchangeable tip-open cell fluorometer of claim 1, wherein saidexcitation source is capable of emitting light having a wavelength fromabout 200 nm to 1200 nm.